1. Field of the Invention
The present invention relates to a battery charging apparatus for charging a high-voltage battery and a low-voltage battery which are installed in, for instance, a hybrid vehicle.
2. Related Art
With a view to environmental preservation and reduction of energy consumption, attention is recently being given to a hybrid vehicle which is fitted with a power system combining an engine and an electric motor. In this hybrid vehicle, the output of the engine is efficiently supplemented in various ways, e.g. the electric motor supplements the output of the engine when accelerating, and the battery is charged by deceleration regeneration and the like when decelerating. The hybrid vehicle is fitted with a high-voltage (e.g. 36 V) battery for supplying electrical energy to the electric motor for driving, and a low-voltage (e.g. 12 V) battery for supplying power to various types of supplementary devices, and a battery charging apparatus for charging both batteries having different voltage specifications is required.
This type of conventional battery charging apparatus will be explained using FIG. 1, described later.
The field-effect transistors Q4 to Q6 shown in FIG. 1 comprise one of the characteristic features of the battery charging apparatus according to the present invention, described below. In the conventional battery charging apparatus explained below, a rectifier (diode) is used instead of the field-effect transistors; together with diodes D1 to D3 and diodes D4 to D6, this diode forms an all-wave rectifier.
In FIG. 1, the ac output of a generator ACG is distributed via a system (open regulator) comprising the diodes D1 to D3 and field-effect transistors Q1 to Q3 to a low-voltage system battery BL, and in addition, is distributed via the diodes D4 to D6 to a high-voltage system battery BH. The ac output of the generator ACG is distributed by controlling the conduction of the field-effect transistors Q1 to Q3, provided in the low-voltage system, in synchronism with the phases of the ac output (U-phase, V-phase, and W-phase) of the generator ACG. That is, as shown in FIG. 4, during the period P1 when the U-phase voltage generated by the generator ACG is high, the field-effect transistor Q1 switches on and becomes conductive, whereby the U-phase output is supplied via the field-effect transistor Q1 to the low-voltage system battery BL.
At this time, the U-phase voltage decreases as it is pulled by the terminal voltage of the low-voltage system battery BL, but the high-voltage system battery BL does not discharge since the rectifer D4 in the high-voltage system is reverse-biased. Thereafter, when the U-phase is inverted in period P2 and the output voltage decreases, the diode D1 becomes reverse-biased. In the conventional apparatus, the battery BL is recharged via an unillustrated diode corresponding to the field-effect transistor Q4.
In period P3, during which the U-phase voltage increases, the field-effect transistor Q1 switches off and becomes nonconductive. This shuts off the power supply to the low-voltage system battery BL, increasing the U-phase voltage from the generator ACG. As a result, the diode D4 becomes sequence-biased, and the power output from the generator ACG is supplied via the diode D4 to the high-voltage system battery BH.
The battery is charged by the V-phase and W-phase outputs in the same manner.
By controlling the field-effect transistors Q1 to Q3 on the low voltage side in this way, it is possible to supplementarily charge the low-voltage and high-voltage systems, enabling both batteries to be charged by a single generator.
Incidentally, the distribution of the phase output of the generator and the like for charging the low-voltage and high-voltage systems is determined as appropriate in accordance with the charge status of the batteries in these systems.
The torque required to rotate the input axis of the generator during charging (hereinafter abbreviated as xe2x80x9cinput torquexe2x80x9d) is determined by the output voltage and output current of the generator, and there is a correlative relationship between the input torque of the generator and the power consumed in charging. When the output voltage of the generator is constant, the greater the charge current, the greater the input torque of the generator; when the output current of the generator is constant, the greater the charge voltage, the greater the input torque of the generator. Applying the rotatory power (e.g. rotary output of an engine), which is generated by the input torque, to the input axis of the generator from the outside generates power comprising electrical energy. Therefore, ideally, when the rotatory power applied to the input axis of the generator is constant, the output voltage and output current should be set so that the output power is constant.
However, in reality, even when a constant rotatory power is applied to the generator, fluctuation in the load changes the output voltage, and consequently, due to the characteristics of the generator, the output current cannot make the output power constant and the output power becomes liable to change. For this reason, as shown in FIG. 4, the size of the input torque T in the period P1, when the low-voltage side battery is being charged, is different from that in the period P3, when the high-voltage side battery is being charged, and the input torque T fluctuates when the output of the generator is distributed to the batteries. As a consequence, the generator produces noise and vibrates, adversely affecting its quietness and durability.
According to the conventional apparatus described above, when for example switching from charging the low-voltage system battery to charging the high-voltage system battery, the output current waveform of the generator becomes distorted. When the current waveform is distorted, the torque required to rotate the input axis of the generator (hereinafter abbreviated as xe2x80x9cinput torquexe2x80x9d) fluctuates. The input torque is determined by the output voltage and output current of the generator, and power comprising electrical energy is generated by applying the rotatory power (e.g. rotary output of an engine), which is generated by the input torque, to the input axis of the generator. Therefore, when the waveform of the output current becomes distorted during charging, the input torque fluctuates, whereby the generator produces noise and vibrates, adversely affecting its quietness and durability.
In FIG. 1, the input axis of the generator ACG is coupled to the output axis of the engine, and the input axis of the generator ACG is rotated by the output of the engine, generating ac output.
According to one method for charging, when the output voltage of the generator is insufficient due to the low number of rotations of the engine, the output of the generator is boosted to obtain the voltage required for charging, and, when the number of rotations of the engine has increased, boosting stops and the battery is charged directly. However, as explained below, according to the battery charging apparatus which uses this type of charging method, when starting and stopping the boosting, the torque required to rotate the input axis of the generator (hereinafter abbreviated as xe2x80x9cinput torquexe2x80x9d) abruptly changes, creating allophones.
The mechanism which generates this type of torque fluctuation will be explained.
FIG. 13 shows characteristics of the input torque and output current (charge current) of the generator with respect to the number of rotations of the input axis. The number of rotations of the generator varies in accordance with the number of rotations of the engine. As shown in FIG. 13, when the output of the generator is increased before charging (boost charging), the voltage required for charging the battery is maintained in the region of low rotation, and the output current of the generator is consumed as charge current, generating input torque in the generator. As the number of rotations increases, the output current of the generator increases, consequently increasing the input torque. Since there is also some loss when switching to boost the voltage, the increase in the output current is restricted.
By contrast, when the battery is charged directly without increasing the output of the generator (direct charging), the voltage required for charging the battery cannot be obtained in the region of low rotation; as a result, the battery cannot be charged and the output current is not consumed as charge current. Therefore, the input torque is a torque which has been generated by factors other than charging, such as the mechanical friction and inertia of the electrical elements. When the number of rotations of the engine is increased until the output voltage is sufficient to charge the battery, the output current becomes charge current. When the number of rotations of the engine is further increased, the output current increases, exceeding the output current during boost charging at intersection B. As the output current increases, the input torque increases also, exceeding the input torque during boost charging at point C. It is possible to switch between boosting and non-boosting, i.e. between boost charging and direct charging, by switching the duty of the boost switching.
Due to the different control statuses when boost charging and direct charging, the number of rotations at the intersection B between the output currents does not necessarily match the number of rotations at intersection C of the input torques. Therefore, with regard to voltage stability of the battery, for example, when the number of rotations R (B) at point B, where the output currents of the generator match, is selected as the number of rotations for switching boosting on/off, the difference Td between the input torques causes the input torque of the generator to abruptly change, generating allophones. In FIG. 14, the number of rotations begins to increase at time t1, and when number of rotations R (B) is reached at time t2, the duty DR of the boost switching is switched. Consequently, the input torque T abruptly fluctuates due to the difference Td in the torques. Similarly, the input torque T abruptly fluctuates when the number of rotations drops and exceeds the number of rotations R (B) at time t6. In this way, the input torque abruptly fluctuates when switching boosting on and off, generating allophones.
In addition to the problems mentioned above, there is a further problem, explained below, that the input torque of the generator fluctuates when the output of the generator is distributed to the low-voltage system battery and the high-voltage system battery, generating noise and vibrations in a similar manner.
The input torque is determined by the output voltage and output current of the generator, and there is a correlative relationship between the input torque of the generator and the power consumed in charging. When the output voltage of the generator is constant, the greater the charge current, the greater the input torque of the generator; when the output current of the generator is constant, the greater the charge voltage, the greater the input torque of the generator. Applying the rotatory power (e.g. rotary output of an engine), which is generated by the input torque, to the input axis of the generator from the outside generates power comprising electrical energy. Therefore, ideally, when the rotatory power applied to the input axis of the generator is constant, the output voltage and output current should be set so that the output power is constant.
However, in reality, even when a constant rotatory power is applied to the generator, fluctuation in the load changes the output voltage, and consequently, due to the characteristics of the generator, the output current cannot make the output power constant and the output power becomes liable to change. For this reason, as shown in FIG. 11, the size of the input torque T in the period P1, when the low-voltage side battery is being charged, is different from that in the period P3, when the high-voltage side battery is being charged, and fluctuates when the output of the generator is distributed to the batteries. As a consequence, the generator produces noise and vibrates, adversely affecting its quietness and durability.
The present invention has been realized in consideration of the above. It is a first object of the present invention to provide a battery charging apparatus in which fluctuation in the input torque of a generator, occuring when the output of a generator is distributed to batteries of a high-voltage system and a low-voltage system, can be effectively reduced, thereby preventing noise and vibration which are caused by fluctuation in the input torque.
The battery charging apparatus of the present invention comprises a generator (corresponding, for example, to a generator ACG explained later) which generates ac power; a first charging system (corresponding, for example, to diodes D1 to D3 and field-effect transistors Q1 to Q3, explained later) which distributes the output of the generator at a timing in synchronism with the output of the generator to a first battery of a low-voltage system, thereby charging the first battery; a second charging system (corresponding, for example, to diode D4 to D6 explained later) which distributes the output of the generator at a timing in synchronism with the output of the generator and different to the timing of charging the first battery to a second battery of a high-voltage system, thereby charging the second battery; and a switch system (corresponding, for example, to field-effect transistors Q4 to Q6 explained later) which chops the output of the generator which is to be distributed to the second battery so as to reduce change in the output power of the generator.
According to this constitution, since the switch system chops the output of the generator, the output voltage of the generator is kept at a sufficient voltage for charging the second battery of the high-voltage system, while the output power of the generator changes. Therefore, by for example setting the chopping ratio appropriately, it is possible to control the input torque of the generator, making the input torque when charging the low-voltage system battery substantially equal to the input torque when charging the high-voltage system battery. Consequently, it is possible to effectively eliminate fluctuation in the input torque of the generator when distributing the output of the generator to the high-voltage system and low-voltage system batteries, preventing noise and vibration caused by fluctuation in the input torque. The switching operation of the switch system may be such as to boost the output of the generator.
In the battery charging apparatus described above, the first charging system comprises a first diode (corresponding, for example, to diodes D1 to D3 explained later), an anode thereof being connected to an output terminal side of the generator and a cathode thereof being connected to an electrode side of the first battery; and a first field-effect transistor (corresponding, for example, to field-effect transistors Q1 to Q3 explained later), provided between the cathode of the first diode and the electrode of the first battery, the first field-effect transistor becoming conductive when the first battery is to be charged and becoming nonconductive when the the battery is to be charged; the second charging system comprising a second diode (corresponding, for example, to diodes D4 to D6 explained later), an anode thereof being connected to an output terminal side of the generator and a cathode thereof being connected to an electrode side of the second battery; and the switch system comprising a second field-effect transistor (corresponding, for example, to field-effect transistors Q4 to Q6 explained later), provided between the output terminal of the generator and ground, the second field-effect transistor switching and chopping the output of the generator based on a clock signal having a duty which is set so as to reduce change in the output power of the generator.
According to this constitution, when the first field-effect transistor turns on and becomes conductive, the first diode becomes sequence-biased, and the output of the generator is distributed via this first diode to the low-voltage system first battery, charging the first battery. On the other hand, when the first field-effect transistor turns off and becomes nonconductive, the output voltage of the generator increases, whereby the second diode becomes sequence-biased, and the output of the generator is distributed via this second diode to the high-voltage system second battery, charging the second battery. At this time, the second field-effect transistor switches based on the clock signal, chopping the output of the generator supplied to the second battery. Therefore, the output power is adjusted so as to eliminate fluctuation in the input torque of the generator.
Further, in the battery charging apparatus described above, the conduction of the second field-effect transistor is controlled in compliance with change in the output phase of the generator when charging the first battery, and based on the clock signal when charging the second battery (corresponding, for example, to a controller CTL explained later)
According to this constitution, when charging the first battery, the first diode and the second field-effect transistor form an all wave rectifier, rectifying all waves of the output of the generator and supplying it to the first battery. Furthermore, when charging the second battery, the second diode and the second field-effect transistor form an all wave rectifier, and the second field-effect transistor functions as a switch system for making the output current of the generator resemble a sine wave. Consequently, the output of the generator can be distributed to the low-voltage system and high-voltage system batteries while reducing fluctuation in the input torque of the generator.
Further, in the battery charging apparatus described above, the generator generates current in multiple phases (corresponding, for example, to three-phase ac current U-phase, V-phase, and W-phase explained later), and the first and second diodes and the first and second field-effect transistors are provided for each of the multiple phases.
According to this constitution, the multiple phases of the generator can be supplied to the batteries along independent charge paths. Consequently, interference and current density in the charge paths can be reduced, stabilizing the charging operation.
The present invention achieves the following effects.
Since the output of the generator to be distributed to the high-voltage system battery is chopped so as to reduce change in the output power of the generator when charging the high-voltage system and the low-voltage system, it is possible to effectively eliminate fluctuation in the input torque of the generator when distributing the output of the generator to the high-voltage system and low-voltage system batteries. Therefore, noise and vibration caused by fluctuation in the input torque can be prevented. Furthermore, since noise and vibration of the generator are prevented, the quietness and durability of the generator are increased.
Further, in the battery charging apparatus described above, the first charging system comprises a first diode, connected between the output terminal side of the generator and the electrode side of the first battery; and a first field-effect transistor, provided between the cathode of the first diode and the electrode of the first battery; the second charging system comprises a second diode, connected between the output terminal side of the generator and the electrode side of the second battery; and the switch system comprises a second field-effect transistor, provided between the output terminal of the generator and ground. Therefore, the output of the generator supplied to the second battery can be chopped, adjusting output power of the generator so as to reduce fluctuation in the input torque of the generator.
Further, in the battery charging apparatus described above, the conduction of the second field-effect transistor is controlled in compliance with change in the output phase of the generator when charging the first battery, and based on the clock signal when charging the second battery. Therefore, the output of the generator can be distributed to the high-voltage system battery and the low-voltage system battery while reducing fluctuation in the input torque of the generator.
Further, in the battery charging apparatus described above, the generator generates current in multiple phases (corresponding, for example, to three-phase ac current U-phase, V-phase, and W-phase explained later), and the first and second diodes and the first and second field-effect transistors are provided for each of the multiple phases. Therefore, the phases of the output of the generator can be supplied to the batteries via independent charge paths. Consequently, interference and current density in the charge paths can be reduced, stabilizing the charging operation.
It is a second object of this invention to reduce distortion in the output current wave form of the generator when distributing the output of the generator to the low-voltage system and high-voltage system batteries, and to prevent noise and vibration, which are caused by such distortion of the output current wave form.
In order to achieve the above object, the present invention has the following constitution.
The battery charging apparatus according to this invention comprises a generator corresponding, for example, to a generator ACG explained later) which generates ac power; a first charging system (corresponding, for example, to diodes D1 to D3 and field-effect transistors Q1 to Q3, explained later) which distributes the output of the generator at a timing in synchronism with the output of the generator to a first battery of a low-voltage system, thereby charging the first battery; a second charging system (corresponding, for example, to diode D4 to D6 explained later) which distributes the output of the generator at a timing in synchronism with the output of the generator, and in the same cycle as the cycle which the first battery is charged in, to a second battery of a high-voltage system, thereby charging the second battery; and a switch system (corresponding, for example, to field-effect transistors Q4 to Q6 explained later) which chops the output of the generator which is to be distributed to the second battery so that the output power wave form of the generator resembles a sine wave.
According to this constitution, since the switch system chops the output of the generator, the output voltage of the generator is kept at a sufficient voltage for charging the second battery of the high-voltage system, while the output current wave form of the generator resembles a sine wave. Therefore, when distributing the output of the generator to the first battery of the low-voltage system and the second battery of the high-voltage system, fluctuation in the input torque, caused by distortion in the output current wave form of the generator, can be reduced, thereby achieving the abovementioned object.
Further, in the battery charging apparatus described above, the first charging system comprises the first charging system comprises a first diode (corresponding, for example, to diodes D1 to D3 explained later), an anode thereof being connected to an output terminal side of the generator and a cathode thereof being connected to an electrode side of the first battery; and a first field-effect transistor (corresponding, for example, to field-effect transistors Q1 to Q3 explained later), provided between the cathode of the first diode and the electrode of the first battery, the first field-effect transistor becoming conductive when the first battery is to be charged and becoming nonconductive when the the battery is to be charged; the second charging system comprises a second diode (corresponding, for example, to diodes D4 to D6 explained later), an anode thereof being connected to an output terminal side of the generator and a cathode thereof being connected to an electrode side of the second battery; and the switch system comprises a second field-effect transistor (corresponding, for example, to field-effect transistors Q4 to Q6 explained later), provided between the output terminal of the generator and ground, the second field-effect transistor switching and chopping the output of the generator based on a clock signal having a duty which is set so that the output power wave form of the generator resembles a sine wave.
According to this constitution, when the first field-effect transistor turns on and becomes conductive, the first diode becomes sequence-biased, and the output of the generator is distributed via this first diode to the low-voltage system first battery, charging the first battery. On the other hand, when the first field-effect transistor turns off and becomes nonconductive, the output voltage of the generator increases, whereby the second diode becomes sequence-biased, and the output of the generator is distributed via this second diode to the high-voltage system second battery, charging the second battery. At this time, the second field-effect transistor switches based on the clock signal, chopping the output of the generator supplied to the second battery. Therefore, the output voltage of the generator is kept at a voltage needed for charging the second battery, while making the output current wave form of the generator in one cycle resemble a sine wave. Therefore, fluctuation in the input torque, caused by distortion in the output current wave form of the generator, is reduced, achieving the first object mentioned above.
Further, in the battery charging apparatus described above, the conduction of the second field-effect transistor is controlled in compliance with change in the output phase of the generator when charging the first battery, and based on the clock signal when charging the second battery.
According to this constitution, when charging the first battery, the first diode and the second field-effect transistor form an all wave rectifier, rectifying all waves of the output of the generator and supplying it to the first battery. Furthermore, when charging the second battery, the second diode and the second field-effect transistor form an all wave rectifier, and the second field-effect transistor functions as a switch system for making the output current of the generator resemble a sine wave. Consequently, the output of the generator can be distributed to the low-voltage system and high-voltage system batteries while reducing fluctuation in the input torque of the generator, caused by distortion in the output current wave form of the generator.
Further, in the battery charging apparatus described above, the generator generates current in multiple phases, (corresponding, for example, to three-phase ac current U-phase, V-phase, and W-phase explained later), and the first and second diodes and the first and second field-effect transistors are provided for each of the multiple phases.
According to this constitution, the phases of the output of the generator can be supplied to the batteries via independent charge paths. Consequently, interference and current density in the charge paths can be reduced, stabilizing the charging operation.
Incidentally, in the battery charging apparatus, the duty of the clock signal may be set so as to reduce change in the output power of the generator.
As a consequence, the input torque when charging the low-voltage system battery becomes substantially equal to the input torque when charging the high-voltage system battery. Therefore, the difference in input torque when charging the low-voltage system and high-voltage system batteries decreases, making it possible to prevent noise and vibration, which are caused by difference in input torque, when distributin the output of the generator to the low-voltage system first battery and the high-voltage system second battery.
The present invention achieves the following effects.
The output of the generator to be distributed to the high-voltage system battery is chopped, so that the output current wave form of the generator resembles a sine wave when charging the high-voltage system and when charging the low-voltage system. Therefore, distortion in the output current wave form of the generator, occuring when the output of the generator is distributed to the high-voltage system and low-voltage system batteries, can be reduced, preventing noise and vibration, which are caused by distortion in the output current wave form. Therefore, noise and vibration, which are caused by fluctuation in the input torque, can be prevented. Further, since noise and vibration of the generator are prevented, the quietness and durability of the generator are increased.
Further, in the battery charging apparatus described above, the first charging system comprises a first diode, connected between the output terminal side of the generator and the electrode side of the first battery; and a first field-effect transistor, provided between the cathode of the first diode and the electrode of the first battery; the second charging system comprises a second diode, connected between the output terminal side of the generator and the electrode side of the second battery; and the switch system comprises a second field-effect transistor, provided between the output terminal of the generator and ground. Therefore, the output of the generator supplied to the second battery can be chopped, adjusting output power of the generator so as to reduce fluctuation in the input torque of the generator.
Further, in the battery charging apparatus described above, the conduction of the second field-effect transistor is controlled in compliance with change in the output phase of the generator when charging the first battery, and based on the clock signal when charging the second battery. Therefore, the output of the generator can be distributed to the high-voltage system battery and the low-voltage system battery while reducing fluctuation in the input torque of the generator.
Further, since the first and second diodes and the first and second field-effect transistors are provided for each of the multiple phases, the phases of the output of the generator can be supplied to the batteries via independent charge paths. Therefore, interference and current density in the charge paths can be reduced, stabilizing the charging operation.
It is a third object of this invention to eliminate abrupt fluctuation in the input torque when switching boosting of the voltage in accordance with the number of rotations of the input axis of the generator, and thereby provide a battery charging apparatus which can reduce noise and vibration caused by such torque fluctuation.
Furthermore, it is a fourth object of the present invention to provide a battery charging apparatus which can effectively reduce fluctuation in the input torque of the generator when distributing the output of the generator to a low-voltage system battery and a high-voltage system battery, and thereby prevent noise and vibration which are caused by such fluctuation in the input torque.
In order to achieve the above objects, the present invention has the following constitution.
The battery charging apparatus comprises a generator corresponding, for example, to a generator ACG explained later) which generates ac power; a first charging system (corresponding, for example, to diodes D1 to D3 and field-effect transistors Q1 to Q3, explained later) which distributes the output of the generator at a timing in synchronism with the output of the generator to a first battery of a low-voltage system, thereby charging the first battery; a second charging system (corresponding, for example, to diodes D4 to D6 explained later) which distributes the output of the generator at a timing in synchronism with the output of the generator and different to the timing of charging the first battery to a second battery of a high-voltage system, thereby charging the second battery; and a switch system (corresponding, for example, to field-effect transistors Q4 to Q6 explained later) which, when the number of rotations of the input axis of the generator is below a number of rotations providing a boundary between boosting and not-boosting the output voltage of the generator, chops and boosts the output of the generator so as to reduce change in the output power of the generator when charging the first battery and when charging the second battery, and, when the number of rotations of the input axis of the generator exceeds the number of rotations providing the boundary, switches the duty of the output of the generator so as to reduce change in the duty.
According to this constitution, when the number of rotations of the input axis of the generator exceeds the number of rotations providing the boundary, the switch system reduces change in the duty of the output of the generator while switching the duty. For example, when the number of rotations of the input axis of the generator increases to a value greater than the number of rotations providing the boundary, the switch system gradually changes the duty of the output of the generator. The output power of the generator gradually changes in accordance with the change in the duty to a value corresponding to the duty which was switched to by the switch system. Therefore, since the output power does not abruptly change, fluctuation in the input torque is smooth, preventing allophones. When the number of rotations increases, the output of the generator increases and the output power changes; however, in this case, the output power changes in compliance with the number of rotations, and therefore does not cause the input torque to fluctuate.
Further, when the number of rotations of the input axis of the generator is below the number of rotations which provides the boundary (i.e. a low number of rotations), the switch system chops the output of the generator and controls the output of the output, keeping the output voltage of the generator at a voltage sufficient for charging the second battery of the high-voltage system, while adjusting the output power of the generator and reducing fluctuation in the input torque. Therefore, by setting the duty of the output of the generator as appropriate, the input torque when charging the low-voltage system and the input torque when charging the high-voltage system can be made substantially equal. Consequently, it is possible to effectively eliminate fluctuation in the input torque of the generator when distributing the output of the generator to the high-voltage system and low-voltage system batteries, preventing noise and vibration caused by fluctuation in the input torque. The switching operation of the switch system may be such as to boost the output of the generator.
Further, in the battery charging apparatus described above, the first charging system comprises a first diode (corresponding, for example, to diodes D1 to D3 and field-effect transistors Q1 to Q3, explained later), an anode thereof being connected to an output terminal side of the generator and a cathode thereof being connected to an electrode side of the first battery, and a first field-effect transistor, provided between the cathode of the first diode and the electrode of the first battery, the first field-effect transistor becoming conductive when the first battery is to be charged and becoming nonconductive when the the battery is to be charged; the second charging system comprises a second diode (corresponding, for example, to diodes D4 to D6 explained later), an anode thereof being connected to an output terminal side of the generator and a cathode thereof being connected to an electrode side of the second battery; and the switch system comprises a second field-effect transistor (corresponding, for example, to field-effect transistors Q4 to Q6 explained later), provided between the output terminal of the generator and ground, the second field-effect transistor switching based on a clock signal having the abovementioned duty and chopping the output of the generator.
According to this constitution, when the first field-effect transistor turns on and becomes conductive, the first diode becomes sequence-biased, and the output of the generator is distributed via this first diode to the low-voltage system first battery, charging the first battery. On the other hand, when the first field-effect transistor turns off and becomes nonconductive, the output voltage of the generator increases, whereby the second diode becomes sequence-biased, and the output of the generator is distributed via this second diode to the high-voltage system second battery, charging the second battery.
At this time, when the number of rotations of the input axis of the generator exceeds the number of rotations providing the boundary, the second field-effect transistor switches based on the clock signal and gradually changes the duty of the output of the generator which is supplied to the second battery. Consequently, the output power of the generator gradually changes. Therefore, even when the duty of the output of the generator is switched in accordance with change in the number of rotations, the output power of the generator changes smoothly and the input torque does not abruptly change, thereby preventing noise and vibration, which are caused by input torque fluctuation.
Furthermore, in the battery charging apparatus described above, the conduction of the second field-effect transistor is controlled in compliance with change in the output phase of the generator when charging the first battery, and based on the clock signal when charging the second battery (corresponding, for example, to the controller CTL explained later).
According to this constitution, when charging the first battery, the first diode and the second field-effect transistor form an all wave rectifier, rectifying all waves of the output of the generator and supplying it to the first battery. Furthermore, when charging the second battery, the second diode and the second field-effect transistor form an all wave rectifier, and the second field-effect transistor functions as a switch system for making the output current of the generator resemble a sine wave. Consequently, the output of the generator can be distributed to the low-voltage system and high-voltage system batteries while reducing fluctuation in the input torque of the generator.
Furthermore, in the battery charging apparatus described above, the generator generates current in multiple phases (corresponding, for example, to three-phase ac current U-phase, V-phase, and W-phase explained later), and the first and second diodes and the first and second field-effect transistors are provided for each of the multiple phases.
According to this constitution, the phases of the output of the generator can be supplied to the batteries via independent charge paths. Consequently, interference and current density in the charge paths can be reduced, stabilizing the charging operation.
The present invention achieves the following effects.
Since the duty of the output of the generator is switched while reducing change therein, it is possible to eliminate abrupt fluctuation in the input torque when switching the boosting of the voltage in accordance with the number of rotations of the input axis of the generator, thereby eliminating noise and vibration caused by such fluctuation in the input torque. Furthermore, change in the output power of the generator when charging the high-voltage system battery and the low-voltage system battery is reduced. Therefore, it is possible to effectively reduce fluctuation in the input torque of the generator when distributing the output of the generator to the high-voltage system and low-voltage system batteries. Therefore, allophones, noise, vibration, and the like, which are caused by fluctuation in the input torque, can be prevented. Furthermore, since noise and vibration of the generator are prevented, the quietness and durability of the generator are increased.
Further, in the battery charging apparatus described above, the first charging system comprises a first diode, connected between the output terminal side of the generator and the electrode side of the first battery, and a first field-effect transistor, provided between the cathode of the first diode and the electrode of the first battery; the second charging system comprises a second diode, connected between the output terminal side of the generator and the electrode side of the second battery; and the switch system comprises a second field-effect transistor, provided between the output terminal of the generator and ground. Therefore, the output of the generator supplied to the second battery can be chopped, adjusting the output power of the generator so as to reduce fluctuation in the input torque of the generator.
Further, in the battery charging apparatus described above, the conduction of the second field-effect transistor is controlled in compliance with change in the output phase of the generator when charging the first battery, and based on the clock signal when charging the second battery. Therefore, the output of the generator can be distributed to the high-voltage system battery and the low-voltage system battery while reducing fluctuation in the input torque of the generator.
Moreover, in the battery charging apparatus described above, the generator generates ac current in multiple phases (corresponding, for example, to three-phases of ac current: U-phase, V-phase, and W-phase, explained later), and the first and second diodes and the first and second field-effect transistors are provided for each of the multiple phases. Consequently, each phase of the output of the generator can be supplied via an independent charge path to the battery. Therefore, interference and current density in the charge paths can be reduced, stabilizing the charging operation.